1. Field of the Invention
This invention is related to the field of storage management and, more particularly, to software used in storage management.
2. Description of the Related Art
In the past, large organizations relied heavily on parallel SCSI technology to provide the performance required for their enterprise data storage needs. More recently, organizations are recognizing that the restrictions imposed by SCSI architecture are too costly for SCSI to continue as a viable solution. Such restrictions include the following:                SCSI disk arrays must be located no more than 25 meters from the host server;        The parallel SCSI bus is susceptible to data errors resulting from slight timing discrepancies or improper port termination; and        SCSI array servicing frequently requires downtime for every disk in the array.        
One solution has been to create technology that enables storage arrays to reside directly on the network, where disk accesses may be made directly rather than through the server's SCSI connection. This network-attached storage (NAS) model eliminates SCSI's restrictive cable distance, signal timing, and termination requirements. However, it adds a significant load to the network, which frequently is already starved for bandwidth. Gigabit Ethernet technology only alleviates this bottleneck for the short term, so a more elegant solution is desirable.
The storage area network (SAN) model places storage on its own dedicated network, removing data storage from both the server-to-disk SCSI bus and the main user network. This dedicated network most commonly uses Fibre Channel technology, a versatile, high-speed transport. The SAN includes one or more hosts that provide a point of interface with LAN users, as well as (in the case of large SANs) one or more fabric switches, SAN hubs and other devices to accommodate a large number of storage devices. The hardware (e.g. fabric switches, hubs, bridges, routers, cables, etc.) that connects workstations and servers to storage devices in a SAN is referred to as a “fabric.” The SAN fabric may enable server-to-storage device connectivity through Fibre Channel switching technology to a wide range of servers and storage devices. The versatility of the SAN model enables organizations to perform tasks that were previously difficult to implement, such as LAN-free and server-free tape backup, storage leasing, and full-motion video services.
In a SAN environment, a path may be defined as a route through a SAN interconnect through which a SAN application communicates with its SAN storage. Determination and selection of optimum paths from storage to SAN applications using the storage may be difficult to achieve, especially in large SANs. SAN configuration may dynamically change, possibly creating bottlenecks, as a SAN grows. Prior art SAN systems may provide mechanisms for static path selection for SAN paths that may let a user select a fixed path manually based on search criteria such as the number of hops. These prior art mechanisms do not proactively monitor path metrics after the manual selection is made, and do not provide the ability to automatically determine and switch to better paths as the SAN changes. Thus, it is desirable to provide a mechanism to proactively identify SAN bottlenecks and to reconfigure SAN pathing “on the fly” to improve the flow of data through the SAN.